1. Field of the Invention
The present invention relates to a capsular endoscope, or more particularly, to a capsular endoscope having an image pickup optical system, image pickup means, and others integrated into a substantially capsule-shaped housing.
2. Description of the Related Art
In the past, endoscope systems have been used in practice and widely adopted for examination or the like of, for example, body cavities. The endoscope system comprises a tubular insertional unit having an image pickup device incorporated in the distal part thereof, an operating unit coupled to the insertional unit, and various pieces of equipment connected to the operating unit including an image processing unit, a display device, and a light source unit or the like. The insertional unit is inserted into a body cavity through a subject's oral cavity or the like in order to observe a desired region in the body cavity. In the conventional endoscope device, a range that can be observed or examined is limited due to restrictions including a restriction on the length of the insertional unit to be inserted into a body cavity.
In recent years, various proposals have been made of a capsular endoscope system comprising: a so-called capsular endoscope that is a compact endoscope having image pickup means which includes an image pickup optical system, illuminating means, communicating means, and power receiving means or a power supply incorporated in a capsule-shaped housing; communicating means for communicating with the capsular endoscope by radio; recording means for recording a received signal; and display means for displaying the received signal on a CRT or an LCD or the like.
When a conventional capsular endoscope is used to examine an intracavitary region, if a lesion or the like is discovered in the subject's body cavity, close examination may be performed using a general-purpose endoscope or the like or predetermined treatment may be performed in addition to the close examination.
In such a case, if accurate positional information representing the position of the lesion discovered through the preceding examination performed using the capsular endoscope were acquired, the lesion would be easily rediscovered during the close examination such as endoscopic examination to be performed later.
Accordingly, various proposals have been made of means for detecting the position of a conventionally proposed capsular endoscope that has been inserted into a body cavity for the purpose of examination and diagnosis. For example, Japanese Unexamined Patent Application Publication No. 2001-46357 has proposed such means.
In a capsular endoscope system disclosed in the Japanese Unexamined Patent Application Publication No. 2001-46357, position detecting means for detecting the position of the capsular endoscope that has been inserted into a body cavity is incorporated in an external receiving device. The position detecting means receives a predetermined signal originating from the capsular endoscope lying in the body cavity, and acquires information on the position of the capsular endoscope in the body cavity on the basis of the strength of the predetermined signal.
However, the position detecting means disclosed in the Japanese Unexamined Patent Application Publication No. 2001-46357 cannot presumably detect the position with satisfactory precision because the signal sent from the capsular endoscope lying in a body cavity is feeble.
Consequently, when close examination or the like is performed later, an operator has to perform labor-intensive work of rediscovering a lesion that is an object of examination and that has been discovered through the previous examination performed using the capsular endoscope.
As mentioned above, when the capsular endoscope is used for examination, if positional information on a lesion discovered through the examination is acquired, the positional information will prove quite helpful. Provision of high-precision positional information is therefore demanded.